Dual three-level phase-shift high-voltage high-power frequency transformer

Abstract

The frequency converter (FC) includes rectification unit (RU), DC unit, two pieces of inversion unit with three electrical levels (IUTEL), and two pieces of LC filtering unit with three phases (FUTP). Positive and negative bus bars of RU are connected to positive and negative ends of DC unit respectively. Two pieces of inversion unit are connected to each other in parallel. Positive bus, negative bus, and neutral point of IUTEL are connected to a group of positive bus, a group of negative bus, and a neutral point of DC unit respectively. The output ends of IUTEL are connected to the input ends of two pieces of LC FUTP respectively. The output ends of two pieces of LC FUTP are connected to two groups of three phase winding taps in electromotor respectively. Based on phase shift of carrier wave, the invention makes frequency of equivalent switch of FC rise one time so as to reduce harmonic content of input voltage of electromotor, and raises efficiency of FC effectively.

Description

technical field [0001] The invention belongs to the technical field of electric transmission, and in particular relates to a double-three-level phase-shifting high-voltage high-power frequency converter. Background technique [0002] With the decrease of non-renewable energy sources, energy saving has become one of the most concerned topics in the world today. Among them, frequency conversion energy saving technology is an important part of modern power electronic technology known as "the crown of energy saving" by the world. [0003] my country's power system is large in scale and there are many thermal power plants. There are a large number of large-capacity medium and high-voltage motors used to drive fans and water pumps, and baffles and valves are often used to adjust the flow. The waste of electric energy is serious. In addition, metallurgy, petroleum, chemical industry, urban A large number of medium and high voltage motors in industries such as water supply, coal, and...

AI Technical Summary

Problems solved by technology

However, the above structure also has disadvantages

[0005] In the two-level inverter directly in series with devices, in order to obtain a better device voltage equalization effect, it is necessary to set a large-capacity resistance-capacitance absorption circuit, thereby reducing the efficiency of the inverter device, and with the increase in the number of series devices , the voltage equalization effect between devices is difficult to be guaranteed

Moreover, in the two-level structure, in order to obtain a better output waveform, the switching frequency of the device is higher, which will further reduce the efficiency of the entire inverter device

In the series multiple inverter, the structure of the split-phase transformer used for rectification is complex, and the structure involves a large number of devices, and the control is complicated

In the three-level frequency converter, according to the current withstand voltage level of the device, if it is to meet the driving requirements of the 6kV voltage level motor in my country, the series connection of two switching devices, the absorption circuit and the static voltage equalizing resistor is required, which makes the frequency conversion The parameter design of each link of the inverter is relatively difficult, and the efficiency of the entire inverter is reduced due to the existence of the resistance-capacity absorption circuit; if the driving requirements of the 10kV motor are to be met, four switching devices, the absorption circuit and the static voltage equalizing resistor are used in series. , which makes the design of the frequency converter more complicated, and it is more difficult to effectively guarantee the voltage equalization effect of the frequency converter, and the loss of the absorption circuit and the static voltage equalization resistance is further increased

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